With a higher theoretical maximum efficiency and a broader effective operational range, Class-D amplifiers are designed to meet the low-power, small size, and growing sound quality requirements for many electronic devices. More specifically, the high power efficiency of Class-D amplifiers translates into less power consumption for a given output power and drastically reduces associated heatsink requirements, which account for an important part of the weight, cost, and size of the electronic device.
Additional design advantages of Class-D amplifiers over other amplifiers, such as Class-A, and AB topologies, include a reduced relative load on the power supply for the same power output. This reduction allows a designer to use a smaller supply. As such, Class-D amplifiers are attractive for low-power, low-cost electronic systems since they offer high efficiency and compact support devices.
Fundamentally, Class-D amplifiers begin the amplification process by translating a received signal over a sampled interval into a pulse modulated signal by operation of switching output devices. In one operational state, current from a power source flows through the switching output devices to generate a pulse output signal. In another operating state, the switching output devices disconnect the power source from the output conduction path and thus behave like an open-circuit so no current should flow from the power source. Class-D amplifiers may use a variety of modulation techniques, such as variations of pulse-width modulation (PWM) and sigma-delta pulse density modulation (PDM), to reduce the amplitude of spectral components at high-frequencies and minimize electromagnetic interference emissions.